1. Field of the Invention
The present invention relates to a semiconductor package terminal inspection apparatus, which inspects PGA, CSP, BGA, QFP, QFJ and a variety of other semiconductor packages for various items such as displacement, pitch, flatness and tip uniformity of the terminals, missing letters, blurredness and displacement of markings indicated (e.g., stamped) on the surfaces of semiconductor packages, and voids inside semiconductor package surfaces.
2. Description of the Related Art
A semiconductor package called a Ball Grid Array (BGA) or Chip Size Package (CSP) (hereafter referred to jointly as BGA), features a 2-dimensional array of ball-shaped solder bumps on the underside surface of the semiconductor package. A BGA is installed on a printed circuit board in such a way that these solder bumps are soldered directly to the printed circuit board.
Conventionally, the inspection of various items such as displacement, pitch and flatness of the terminals in semiconductor packages of the type which the terminals are formed on the underside surface of the package as with BGA, was performed by means of a laser displacement measuring instrument which measures the distance to an inspection object using a triangulation principle.
With the abovementioned conventional technique, a laser displacement measuring instrument is positioned over the semiconductor package, which is arranged with the underside surface up, and the height of each solder bump was measured by using this laser displacement measuring instrument to scan one-by-one the vicinity of the top of each solder bump of the semiconductor package.
In conventional techniques that use a laser displacement measuring instrument, since the laser displacement measuring instrument measures the height of each solder bump one-by-one, inspection takes a long time, and if there is a scratch or the like on the surface of a solder bump, accurate inspection measurements cannot be achieved.
The specification of Japanese patent application No.8-124953 discloses a technique to solve the above-described problems. FIG. 8 shows the configuration of the apparatus according to this technique.
In FIG. 8, a BGA 1 is turned upside-down and placed on top of a BGA tray 3, a half mirror 4 is positioned over top of the BGA 1, and an illumination 5 for a camera A is positioned thereabove. Camera A images a plan view of the underside surface of BGA 1 via half mirror 4. An illumination 6 for a camera B is set up to the side of BGA 1, and camera B images, obliquely from above, the underside surface of BGA 1 where the balls (solder bumps) 2 are arrayed.
In the technology depicted in the FIG. 8, 3-dimensional information (plan location (x-y locations) and height (z location)) on each ball is obtained based on image data picked up by two cameras A, B. However, optimal imaging is not possible with each camera A, B when both illuminations 5, 6 are on at the same time. Therefore, it is required that, when imaging with camera A, only camera A illumination 5 is turned on, and when imaging with camera B, only camera B illumination 6 is turned on.
Thus, with the technology depicted in the FIG. 8, two cameras A, B must be operated alternately. Therefore, imaging takes time, and efficient inspection cannot be achieved.
Furthermore, when BGA with large dimensions is inspected or when high resolution is required, the image area of BGA is too large compared with the field of view of a camera. Therefore, in order to image BGA with a single imaging operation, two or more cameras must be installed. However, because BGA is smaller than the cameras, when these two cameras are set up side by side and imaging of the BGA is attempted, interference occurs between the cameras.
Furthermore, in addition to the inspection of the leads (terminals), semiconductor package inspections include the inspections for missing letters, blurredness and displacement of the markings (such as manufacturer's name and manufacturing number) indicated onto the upper surface of a package, and inspected for defects, such as voids occurring in a package. During these inspections as well, a camera and illumination are used in the same way as described above.
Because the optimal positioning of the illumination for these inspections differs from the illumination position for lead inspection, these inspections had to be performed separately from the lead inspection.